Rising temperatures make mockery of rising scepticism

Tim Flannery

With record-breaking extreme weather causing havoc around the nation, it's important that Australians understand what climate scientists are saying about the climate in future. But the conflation of two aspects of climate information is misleading the public, either maliciously or carelessly.

The first concerns average temperatures, the second what's happening at the extremes. These are different aspects of climate change, and climate scientists deal with them using different methods.

Is the world warming or cooling? This is a question about average temperature, and the answer can only be found by examining many decades of climate records. That's because there's a lot of annual variability in average temperatures.

By selectively choosing a few years of records, you can tell any story you want. But the trend over the longer term is undeniable. The world is warming, and Australia is 0.9 of a degree Celsius warmer than it was a century ago.

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Editors know that headlines tell the story, which is why it's concerning that The Australian chose the headline ''Climate results validate sceptics'' for an article on the British Met Bureau's latest four-year forecast. Here is what the forecast in fact said: ''Global average temperature is expected to remain between 0.28°C and 0.59°C (90 per cent confidence range) above the long-term (1971-2000) average during the period 2013-2017, with values most likely to be about 0.43°C higher than average . . . This means temperatures will remain well above the long-term average and we will continue to see temperatures like those which resulted in 2000-2009 being the warmest decade in the instrumental record dating back to 1850.''

The spin matters. If Australians believe that the warming trend is over, and are suspicious of meteorological reports, they are likely to be less well prepared for extreme weather.

The evidence for an increase in such weather is clear. The CSIRO and Bureau of Meteorology have reported that Australia has experienced fewer very cold days and more very hot days than it did 50 years ago.

The current heatwave is breaking many temperature records. The nation's hottest day occurred on Monday, January 7. For seven days in a row, from January 2-8, the average maximum temperature across Australia was above 39 degrees. And with the extreme heat has come bushfires, destruction, health problems, and disruption of infrastructure.

Record-breaking heat is, by definition, weather not experienced for as long as records have been kept. But it's not just unprecedented heat the nation is facing.

In 2011, sea-surface temperatures to the north-west of Australia reached record highs. Increased water evaporation contributed to the wettest year on record in Australia. The vegetation of the inland flourished. But then the region experienced its longest period ever without rain, drying the vegetation. Now, the record heatwave is allowing fires to flourish.

It's a chain of climatic extremes that can have deadly consequences.

Climate sceptics are trying to play down the significance of these events. This weekend the Climate Commission published a report by some of Australia's most eminent climate scientists on the connection between climate change and the extreme heat Australia is experiencing.

The report concluded that: "The length, extent and severity of this heatwave are unprecedented in the measurement record. Although Australia has always had heatwaves, hot days and bushfires, climate change has increased the risk of more intense heatwaves and extreme hot days, as well as exacerbated bushfire conditions. Scientists have concluded that climate change is making extreme hot days, heatwaves and bushfire weather worse."

Extreme weather events are important because of the danger they can present. They are also a sign that the range of weather we experience is shifting. Good community understanding of climate change risks is critical to ensure we take appropriate action to reduce greenhouse gas emissions and to put measures in place to prepare for, and respond to, extreme weather.

Australia is not alone in experiencing record-breaking extremes. Last July in the US, more than 3000 temperature records fell as extreme heat and drought gripped North America. The climate scientists have been predicting events like this for decades. And yet still the sceptics ignore the evidence.

Professor Tim Flannery is chief commissioner of the Climate Commission.

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